Micro-fluid ejection heads are useful for ejecting a variety of fluids including inks, cooling fluids, pharmaceuticals, lubricants and the like. A widely used micro-fluid ejection head is in an ink jet printer. Ink jet printers continue to be improved as the technology for making the micro-fluid ejection heads continues to advance. New techniques are constantly being developed to provide low cost, highly reliable printers which approach the speed and quality of laser printers. An added benefit of ink jet printers is that color images can be produced at a fraction of the cost of laser printers with as good or better quality than laser printers. All of the foregoing benefits exhibited by ink jet printers have also increased the competitiveness of suppliers to provide comparable printers and supplies for such printers in a more costs efficient manner than their competitors.
An illustrative micro-fluid ejection device is illustrated in FIG. 1. The micro-fluid ejection device includes an integral fluid reservoir 10 for holding fluid to be ejected from a micro-fluid ejection head 12 that is attached to a head portion 14 of the fluid reservoir 10. The geometry of a prior art head portion 14 of the fluid reservoir 10, as shown in FIGS. 2 and 3 (prior art), may include features such as a substrate cavity 16 with a length and width designed to provide sufficient space to fixedly attach and seal a substrate 18 in the cavity 16 with a die bond adhesive, and may seal a TAB circuit 34 to the fluid reservoir 10 with a die bond adhesive in vent channels 27A and 27B on a deck 36. The substrate cavity 16 has at least one fluid supply slot (each referred to hereinafter as a via 20) disposed therein, and may have two or more vias 20 in a floor portion 22 of the cavity 16 for permitting fluid to flow from the reservoir 10 to the substrate 18 when the micro-fluid ejection head 12 is used. The vias 20 typically contain narrow walls (sometimes referred to herein as “racetracks” 24) adjacent at least one side 26 thereof for spacing the substrate 18 from the floor portion 22 of the cavity 16. The narrow walls 24 provide room for the die bond adhesive to secure the substrate 18 in the substrate cavity 16 and to provide sufficient adhesive seal against the substrate 18 to prevent fluid leakage out of the cavity 16 and/or vias 20.
In order to provide adequate flow of adhesive throughout the substrate cavity 16, and to properly seal the TAB circuit 34 to the fluid reservoir 10, vents 27A and 27B leading to external vent channels 28 and 30 are located on opposing sides of the substrate cavity 16. The vents 27A and 27B can direct the adhesive and associated gasses (e.g., outgasses and volatiles) from the substrate cavity 16 so that it may seal against the back side 32 of a TAB circuit 34, which is used to operatively connect the substrate 18 to a micro-fluid ejection control device such as a printer. The vents 27A and 27B also provide adhesive flow to external vent channels 28 and 30 that help to minimize gas bubbles in the adhesive as the adhesive wicks into the vents 27A and 27B and vent channels 28 and 30 and cures. The adhesive is also effective to seal the external vent channels 28 and 30 so that fluid from the substrate cavity 16 may not escape through the vents 27A and 27B and vent channels 28 and 30 after the adhesive has cured. Typically, vents 27A and 27B have a periodic spacing 29 along a length of the substrate cavity of about 2 millimeters.
Conventionally, the volume of adhesive in the substrate cavity 16 and in the vents 27A and 27B and vent channels 28 and 30 is critical to providing suitable corrosion protection for a back side 32 of the TAB circuit 34 that is attached to a substantially planar surface 36 of the head portion 14 of the fluid reservoir 10. Too much adhesive in the vent channels 28 and 30 may affect TAB circuit 34 topography, as described in more detail below, thereby reducing the performance of the micro-fluid ejection head. Inadequate sealing of the back side 32 of the TAB circuit 34 due to adhesive location, or the presence of gas bubbles in the adhesive, should be minimized. While the vents 27A and 27B and vent channels 28 and 30 have provided some improvement in the ability to seal the back side 32 of the TAB circuit 34, gas bubbles and adhesive topography, for example, continue to be a problem. Accordingly, there continues to be a need for methods and apparatus that, among other things, increase adhesion area and/or increase gas venting capabilities during assembly of micro-fluid ejection devices. In view of the foregoing and/or other reasons, exemplary embodiments of the disclosure provide fluid ejection head assemblies, fluid ejection devices, and methods for improving fluid sealing of fluid ejection head assemblies. One such fluid ejection head assembly includes a substrate cavity and a substantially planar surface surrounding the substrate cavity. The substantially planar surface contains at least one external vent, at least one internal vent channel, and a plurality of vents in fluid flow communication with the substrate cavity and providing fluid flow communication between the internal vent channel and the external vent. The plurality of vents, the at least one external vent and the at least one internal vent channel are disposed in fluid flow communication with an environment external to the substrate cavity for flow of a gas associated with an adhesive at least partially disposed in at least one of the substrate cavity and the at least one internal vent channel, to the environment during the curing of the adhesive.
In another embodiment there is provided a method for improving sealing between a circuit, such as a TAB circuit, and a fluid ejection assembly. The fluid ejection assembly has a substantially planar surface, a substrate cavity, and a vent system placing the substrate cavity in fluid flow communication with an environment external to the substrate cavity. The vent system includes an internal vent channel, an external vent, and a plurality of connecting vent channels connecting the internal vent channel and the external vent to one another. An amount of adhesive is disposed in the substrate cavity and in the internal vent channel sufficient to substantially attach and to substantially seal a substrate in the substrate cavity, and to substantially seal a backside of a circuit (e.g., to the fluid ejection assembly), thereby enhancing corrosion protection of lead beams on the circuit.
Still another embodiment provides a method for improving sealing between a circuit and a fluid ejection assembly. The fluid ejection assembly has a substantially planar surface substantially surrounding a recessed substrate cavity, and a vent system in the substantially planar surface. The vent system is in fluid flow communication with the substrate cavity. The vent system includes at least one external vent, at least one internal vent channel disposed between the external vent and the substrate cavity, and a plurality of connecting vent channels orthogonal to the internal vent channels. The connecting vent channels are in fluid flow communication with the substrate cavity, the internal vent channel and the external vent. An adhesive is disposed in at least one of the substrate cavity and the internal vent channel to substantially fill the substrate cavity and flow into the vent system. A micro-fluid ejection head is attached to the adhesive in the substrate cavity. A circuit is attached to the micro-fluid ejection head and at least a portion of the substantially planar surface. The adhesive is cured.
Yet another embodiment provides a micro-fluid ejection head device including a recessed substrate cavity. A substantially planar surface substantially surrounds the substrate cavity. A vent system is disposed in the substantially planar surface in fluid flow communication with the substrate cavity and an environment external to the substrate cavity. The vent system includes an internal vent channel, an external vent, and a plurality of connecting channels orthogonal to the internal vent channel. The connecting vent channels are in fluid flow communication with the substrate cavity, the internal vent channel and the external vent.